Dissolved inorganic nitrogen (DIN)

Dissolved inorganic nitrogen (DIN) Key Message HELCOM core indicator report July 2017 The core indicator evaluates average dissolved inorganic nitrogen concentration in the surface (0 10 m) during winter (December February) during the assessment period 2011-2015. Of the 17 assessed open-sea assessment units, good status has been achieved only in the Gdansk Basin (DIN concentration below defined threshold value, which reflects good conditions).though the winter-time DIN is still at elevated levels in the remaining 16 sub-basins, it has decreased in the 1990s or the early 2000s and remained since then on the same level. Key message figure 1: Status assessment results based evaluation of the indicator DIN'. The assessment is carried out using Scale 4 HELCOM assessment units (defined in the HELCOM Monitoring and Assessment Strategy Annex 4). The confidence of the presented DIN status estimate is moderate in all 17 open sub-basins. Of all coastal waters where DIN was assessed, good eutrophication status was only found in Polish coastal waters and around the Swedish islands in Gotland Basin. The indicator is applicable in the waters of all countries bordering the Baltic Sea. www.helcom.fi > Baltic Sea trends > Indicators HELCOM 1

Relevance of the core indicator Eutrophication is caused by excessive inputs of nutrients (nitrogen and phosphorus) resulting from various human activities. High concentrations of nutrients and their ratios form the preconditions for huge algal blooms, reduced water clarity and increased oxygen consumption. Long-term nutrient data are key parameters for quantifying the effects of anthropogenic activities and evaluating the success of measures undertaken. Policy relevance of the core indicator BSAP Segment and Objectives MSFD Descriptors and Criteria Primary link Baltic Sea unaffected by eutrophication D5 Human-induced eutrophication - D5C1 Nutrient concentrations are not at levels that indicate adverse eutrophication effects Secondary link Other relevant legislation: EU Water Framework Directive D1 Biological diversity of species and habitats Theme: Pelagic habitats -D1C6 The condition of the habitat type, including its biotic and abiotic structure and its functions, is not adversely affected due to anthropogenic pressures. Theme: Benthic habitats -D6C5 The extent of adverse effects from anthropogenic pressures on the condition of the habitat type, including alteration to its biotic and abiotic structure and its functions, does not exceed a specified proportion of the natural extent of the benthic habitat type in the assessment area. Cite this indicator HELCOM (2017). Dissolved inorganic nitrogen (DIN). HELCOM core indicator report. Online. [Date Viewed], [Web link]. ISSN 2343-2543 Download full indicator report HOLAS II component - Core indicator report web-based version July 2017 (pdf) www.helcom.fi > Baltic Sea trends > Indicators HELCOM 2

Results and Confidence Current status of the Baltic Sea DIN concentration Of 17 open-sea sub-basins, good status (concentrations below threshold) for nitrogen (DIN) has been achieved only in the Gulf of Gdansk (Results figure 1). The sub-basin causing greatest concern regarding nitrogen status is the Gulf of Finland, Gulf of Riga, and Bornholm Basin. The status of Kattegat, Great Belt, Kiel Bay, eastern and western Gotland Basin, Åland Sea, Bothnia Sea, the Quark and Bothnian Bay are only slightly above threshold values. Of all coastal waters where DIN was assessed, Good eutrophication status was only found in coastal waters of Poland and around the Swedish islands in Gotland Basin. Results Figure1. Status of the DIN indicator, presented as eutrophication ratio (ER). ER shows the present concentration in relation to the threshold value, increasing along with increasing eutrophication. The threshold value is ER 1.00. www.helcom.fi > Baltic Sea trends > Indicators HELCOM 3

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Results figure 2. Winter DIN concentration (black line; average for 2011-2015) and threshold values as agreed by HELCOM HOD 39/2012 (red broken line). It should be noted that the results for Bornholm Basin strongly depend on stations in the open-sea area of Pomeranian Bay, which is influenced by the Odra plume. The low concentration value in Gulf of Gdansk in 2011 are due to data handling problems. The issue is being investigated and is planned to be rectified for the next update of this indicator report. Results table 1. Threshold values, present concentration (as average 2011-2015), eutrophication ratio (ER) and status of DIN in the open-sea basins. ER is a quantitative value for the level of eutrophication, calculated as the ratio between the threshold value and the present concentration when ER > 1, threshold value has not been reached. Assessment unit (open sea) Threshold value (µmol l -1 ) Average 2011-2015 (µmol l -1 ) Eutrophication ratio, ER Status (fail/achieved threshold value) Kattegat 5.00 5.84 1.168 fail Great Belt 5.00 5.30 1.059 fail The Sound 3.30 5.60 1.697 fail Kiel Bay 5.50 5.88 1.068 fail Bay of Mecklenburg 4.30 6.41 1.491 fail Arkona Basin 2.90 4.05 1.397 fail Bornholm Basin 2.50 9.06 3.626 fail Eastern Gotland Basin 2.60 3.30 1.269 fail Gdansk Basin 4.20 3.03 0.721 achieve Western Gotland Basin 2.00 2.92 1.460 fail Northern Baltic Proper 2.90 4.86 1.677 fail Gulf of Riga 5.20 10.75 2.067 fail Gulf of Finland 3.80 8.98 2.362 fail Aland Sea 2.70 3.90 1.443 fail Bothnian Sea 2.80 3.87 1.381 fail The Quark 3.70 4.72 1.275 fail Bothnian Bay 5.20 6.46 1.242 fail www.helcom.fi > Baltic Sea trends > Indicators HELCOM 5

Long-term trends The long-term trends are provided as additional information and do not influence the status assessment. It should be noted that the information is not presented in the HELCOM assessment units, but for areas as defined in the BALTSEM model. Though the wintertime DIN is still at elevated levels in the remaining 16 sub-basins, it decreased in the 1990s or the early 2000s and has since then remained on the same level. www.helcom.fi > Baltic Sea trends > Indicators HELCOM 6

Result figure 3. Long-term trends of DIN in the BALTSEM basins (see BSEP 133) for 1970-2015. The spatial and seasonal patterns of historical are separated across the years, using a GLM-GAM model according to Carstensen et al. 2006. The data until 2012 is from TARGREV project and data for 2013-2015 has been based on data extraction from the assessment database. Lines represent standard errors (SE). Confidence of the indicator status evaluation The confidence of the indicator status estimate in open sea areas, based on the spatial and temporal coverage of data as well as the accuracy of the protocol for setting threshold values, was moderate in all sub-basins. www.helcom.fi > Baltic Sea trends > Indicators HELCOM 7

Results figure 4. Indicator confidence, determined combining information on data availability and the accuracy of the protocol for setting threshold values. Low indicator confidence calls for increase in monitoring. The indicator confidence was estimated through confidence scoring of the threshold value (ET-Score) and the indicator data (ES-Score). The ET-Score was rated based on the uncertainty of the threshold value setting procedure. The ES-Score is based on the number as well as spatial and temporal coverage of the observations for the assessment period 2011-2015. To estimate the overall indicator confidence, the ETand ES-Scores were combined. See Andersen et al. 2010 and Fleming-Lehtinen et al. 2015 for further details. www.helcom.fi > Baltic Sea trends > Indicators HELCOM 8

Good Environmental Status Good environmental status is measured in relation to scientifically based and commonly agreed sub-basinwise threshold value, which defines the concentration that should not be exceeded (Good Environmental Status figure 1). Good environmental status figure 1. Schematic representation of the threshold value applied in the DIN core indicator, the threshold values are assessment unit specific (see Good environmental status table 1). These indicator threshold values were based on the results obtained in the TARGREV project (HELCOM 2013a), taking also advantage of the work carried out during the EUTRO PRO process (HELCOM 2009) and national work for EU WFD. The final threshold values were set through an expert evaluation process done by the intersessional activity on development of core eutrophication indicators (HELCOM CORE EUTRO) and the threshold values were adopted by the HELCOM Heads of Delegations 39/2012. Good environmental status table 1. Assessment unit specific threshold values for the DIN core indicator. HELCOM_ID Assessment unit (open sea) Threshold value (μmol l 1 ) SEA-001 Kattegat 5.00 SEA-002 Great Belt 5.00 SEA-003 The Sound 3.30 SEA-004 Kiel Bay 5.50 SEA-005 Bay of Mecklenburg 4.30 SEA-006 Arkona Sea 2.90 SEA-007 Bornholm Sea 2.50 SEA-008 Eastern Gotland Basin 4.20 SEA-009 Gdansk Basin 2.60 SEA-010 Western Gotland Basin 2.00 SEA-011 Northern Baltic Proper 5.20 SEA-012 Gulf of Riga 2.90 SEA-013 Gulf of Finland 3.80 SEA-014 Åland Sea 2.70 SEA-015 Bothnian Sea 2.80 SEA-016 The Quark 3.70 SEA-017 Bothnian Bay 5.20 www.helcom.fi > Baltic Sea trends > Indicators HELCOM 9

Assessment Protocol This core indicator are updated using data reported by Contracting Parties to the HELCOM COMBINE database hosted by ICES, using the algorithms developed for the eutrophication assessment work flow. The values are achieved using indicators specifications shown in Assessment protocol table 1 (see HELCOM Eutrophication assessment manual). Assessment protocol table 1. Specifications of the indicator DIN. Indicator Response to eutrophication Parameters Data source Assessment period (test assessment) Assessment season Depth Removing outliers Removing close observations Indicator level Eutrophication ratio (ER) Status confidence (ES- Score) Indicator threshold value confidence Indicator confidence (I- Score) DIN Positive DIN = NO2 + NO3 + NH4 concentration (µm/l) Monitoring data provided by the HELCOM Contracting Parties, and kept in the HELCOM COMBINE database, hosted by ICES (www.ices.dk) December 2010 February 2015 Winter = December + January + February Surface = average in the 0 10 m layer No outliers removed No close observations removed average of yearly average values ER = ES / ET LOW (=0%), if no more than 5 annual status observations are found during one or more years. MODERATE (=50%), if more than 5 but no more than 15 status observations are found per year. HIGH (=100%), if more than 15 spatially non-biased status observations are found each year. MODERATE Confidence (%) = average of ES-Score and ET-Score www.helcom.fi > Baltic Sea trends > Indicators HELCOM 10

The indicators within the criteria were weighted according to their relevance for eutrophication in each sub-basin. Assessment units The core indicator is applicable in the 17 open sea assessment units (at least one nautical mile seawards from the baseline). In the coastal units, the indicator is assessed using comparable indicators developed nationally for the purposes of assessments under the EU Water Framework Directive. The assessment units are defined in the HELCOM Monitoring and Assessment Strategy Annex 4. www.helcom.fi > Baltic Sea trends > Indicators HELCOM 11

Relevance of the Indicator Eutrophication assessment The status of eutrophication is assessed using several core indicators. Each indicator focuses on one important aspect of the complex issue. In addition to providing an indicator-based evaluation of the dissolved inorganic nitrogen, this indicator contributes to the overall eutrophication assessment along with the other eutrophication core indicators. Policy relevance Eutrophication is one of the four thematic segments of the HELCOM Baltic Sea Action Plan (BSAP) with the strategic goal of having a Baltic Sea unaffected by eutrophication (HELCOM 2007). Eutrophication is defined in the BSAP as a condition in an aquatic ecosystem where high nutrient concentrations stimulate the growth of algae, which leads to imbalanced functioning of the system. Nutrient concentrations in the water column are caused by increased anthropogenic nutrient loads from land and air. The goal for eutrophication is broken down into five ecological objectives, of which one is concentrations of nutrients close to natural levels. The EU Marine Strategy Framework Directive (Anonymous 2008) requires that human-induced eutrophication is minimized, especially adverse effects thereof, such as losses in biodiversity, ecosystem degradation, harmful algal blooms and oxygen deficiency in bottom waters (Descriptor 5). Nutrients in the watercolumn (including DIN) are determined as the criteria elements for assessing eutrophication under the criterion D5C1 Nutrient concentrations are not at levels that indicate adverse eutrophication effects. The EU Water Framework Directive (Anonymous 2000) requires good ecological status in the European coastal waters. Good ecological status is defined in Annex V of the Water Framework Directive, in terms of the quality of the biological community, the hydrological characteristics and the chemical characteristics, including nitrogen concentration. Role of dissolved inorganic nitrogen (DIN) in the ecosystem Marine eutrophication is mainly caused by nutrient enrichment leading to increased production of organic matter supplied to the Baltic Sea with subsequent effects on water transparency, phytoplankton communities, benthic fauna and vegetation as well as oxygen conditions. Phytoplankton as well as benthic vegetation need nutrients, mainly nitrogen and phosphorus, for growth. www.helcom.fi > Baltic Sea trends > Indicators HELCOM 12

Relevance figure 1. Simplified conceptual model for N and P nutrients in the Baltic Sea, where DIN = Dissolved inorganic nitrogen, TN = Total nitrogen, DIP = Dissolved inorganic phosphorus and TP = Total phosphorus. Flows along arrows into the blue sea area tend to increase concentrations, and flows along arrows out from the sea act in the opposite direction. Management refers to nutrient load reductions. Human pressures linked to the indicator General MSFD Annex III, Table 2 Strong link Weak link Substances, litter and energy - Input of nutrients diffuse sources, point sources, atmospheric deposition Nutrient concentrations in the water column are affected by increased anthropogenic nutrient loads from land and air. www.helcom.fi > Baltic Sea trends > Indicators HELCOM 13

Monitoring Requirements Monitoring methodology Monitoring of nitrogen concentration in the Contracting Parties of HELCOM is described on a general level in the HELCOM Monitoring Manual in the sub-programme Nutrients. Monitoring guidelines specifying the sampling strategies for nitrate, nitrite and ammonium are adopted and published. Current monitoring The monitoring activities relevant to the indicator that are currently carried out by HELCOM Contracting Parties are described in the HELCOM Monitoring Manual sub-programme Nutrients monitoring concepts table Description of optimal monitoring Regional monitoring of dissolved organic nitrogen is considered sufficient to support the indicator evaluation. www.helcom.fi > Baltic Sea trends > Indicators HELCOM 14

Data and updating Access and use The data and resulting data products (tables, figures and maps) available on the indicator web page can be used freely given that the source is cited. The indicator should be cited as following: HELCOM (2017) Dissolved inorganic nitrogen (DIN). HELCOM core indicator report. Online. [Date Viewed], [Web link]. ISSN 2343-2543 Result: Dissolved inorganic nitrogen Metadata Data source: The average for 2011-2015 was estimated using monitoring data provided by the HELCOM Contracting Parties, and kept in the HELCOM COMBINE database, hosted by ICES (www.ices.dk). Nominated members of HELCOM STATE & CONSERVATION group were given the opportunity to review the data, and to supply any missing monitoring observations, in order to achieve a complete dataset. Description of data: The data include the sum of in-situ NO 2 and NO 3 samples, determined using colorimetric methods, as explained in the HELCOM COMBINE manual. Measurements made at the depth of 0 10 m from the surface were used in the assessment. Geographical coverage: The observations are distributed in the sub-basins according to the HELCOM COMBINE programme, added occasionally with data from research cruises. Temporal coverage: The raw data includes observations throughout the year, during the assessment period 2011-2015. Data aggregation: The 2011-2015 averages for each sub-basin were produced as an inter-annual winter (December-February) estimates. www.helcom.fi > Baltic Sea trends > Indicators HELCOM 15

Contributors and references Vivi Fleming-Lehtinen 1, Elżbieta Łysiak-Pastuszak 2, Marina Carstens 3, Wera Leujak 4, Günther Nausch 5, Joni Kaitaranta 6, Laura Hoikkala 6, Minna Pyhälä 6 1 Finnish Environment Institute, SYKE, Finland 2 Institute of Meteorology and Water Management, National Research Institute, Poland 3 State Agency for Environment, Nature Protection and Geology Mecklenburg-Vorpommern, Germany 4 German Federal Environment Agency, Germany 5 Leibniz Institute for Baltic Sea Research Warnemünde (IOW), Germany 6 Secretariat of the Helsinki Commission HELCOM Expert Network on Eutrophication Archive This version of the HELCOM core indicator report was published in July 2017: HOLAS II component - Core indicator report web-based version July 2017 (pdf) Older versions of the core indicator report are available: DIN concentrations 2007-2011 (pdf) Nutrient concentrations 2003-2007 - HELCOM Core Indicator Report (pdf) References Andersen, J. H., Murray, C., Kaartokallio, H., Axe, P. & Molvær, J. (2010). Confidence rating of eutrophication status classification. Marine Pollution Bulletin 60, 919 924. Anonymous (2008) Directive 2008/56/EC of the European Parliament and of the Council. 17 June 2008. Establishing a Framework for Community Action in the Field of Marine Environmental Policy. Marine Strategy Framework Directive. 22p. Anonymous (2000). Directive 200/60/EC of the European parliament and of the council of 23 October 2000 establishing a framework for community action in the field of water policy. Official Journal of the European Communities L 327/1. Carstensen J, D.J. Conley, J.H. Andersen, G. Ærtebjerg (2006). Coastal eutrophication and trend reversal: a Danish case study. Limnology & Oceanography 51:398-408. Fleming-Lehtinen, V., Andersen, J. H., Carstensen, J., Łysiak-Pastuszak, E., Murray, C., Pyhälä, M. & Laamanen, M. (2015). Recent developments in assessment methodology reveal that the Baltic Sea eutrophication problem is expanding. Ecological Indicators 48, 380 388. HELCOM (2007) Baltic Sea Action Plan. Baltic Sea Environment Protection Commission. 101p. www.helcom.fi > Baltic Sea trends > Indicators HELCOM 16

HELCOM (2013) Approaches and methods for eutrophication target setting in the Baltic Sea region. Balt. Sea Environ. Proc. No. 133 Additional relevant publications Eutrophication status of the Baltic Sea 2007-2011 - A concise thematic assessment (2014) Approaches and methods for eutrophication target setting in the Baltic Sea region (2013) HELCOM core indicators. Final report of the HELCOM CORESET project (2013) Eutrophication in the Baltic Sea. An integrated thematic assessment of the effects of nutrient enrichment in the Baltic Sea region (2009) Development of tools for assessment of eutrophication in the Baltic Sea (2006) HELCOM core indicator report, ISSN 2343-2543 www.helcom.fi > Baltic Sea trends > Indicators HELCOM 17